The Computer Language
22.05 Benchmarks Game

n-body C# .NET #8 program

source code

  /*  The Computer Language Benchmarks Game
      https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

      contributed by Isaac Gouy
      modified by Robert F. Tobler
      modified by Eric P. Nusbaum
  */
  
  using System;

  public class NBody {
    public static void Main(String[] args) {
      int n = args.Length > 0 ? Int32.Parse(args[0]) : 10000;
      NBodySystem bodies = new NBodySystem();
      Console.WriteLine("{0:f9}", bodies.Energy());
      for (int i = 0; i < n; i++) bodies.Advance(0.01);
      Console.WriteLine("{0:f9}", bodies.Energy());
    }
  }

  public class Body { public double x, y, z, vx, vy, vz, mass; }

  public class NBodySystem {
    private Body[] _bodies;
    private Body[] _pairL;
    private Body[] _pairR;
    private byte bodyCount = 5;

    const double Pi = 3.141592653589793;
    const double Solarmass = 4 * Pi * Pi;
    const double DaysPeryear = 365.24;

    public NBodySystem() {
      _bodies = new[] {
        new Body()
        {
            // Sun
            mass = Solarmass,
        },
        new Body()
        {
            // Jupiter
            x = 4.84143144246472090e+00,
            y = -1.16032004402742839e+00,
            z = -1.03622044471123109e-01,
            vx = 1.66007664274403694e-03*DaysPeryear,
            vy = 7.69901118419740425e-03*DaysPeryear,
            vz = -6.90460016972063023e-05*DaysPeryear,
            mass = 9.54791938424326609e-04*Solarmass,
        },
        new Body()
        {
            // Saturn
            x = 8.34336671824457987e+00,
            y = 4.12479856412430479e+00,
            z = -4.03523417114321381e-01,
            vx = -2.76742510726862411e-03*DaysPeryear,
            vy = 4.99852801234917238e-03*DaysPeryear,
            vz = 2.30417297573763929e-05*DaysPeryear,
            mass = 2.85885980666130812e-04*Solarmass,
        },
        new Body()
        {
            // Uranus
            x = 1.28943695621391310e+01,
            y = -1.51111514016986312e+01,
            z = -2.23307578892655734e-01,
            vx = 2.96460137564761618e-03*DaysPeryear,
            vy = 2.37847173959480950e-03*DaysPeryear,
            vz = -2.96589568540237556e-05*DaysPeryear,
            mass = 4.36624404335156298e-05*Solarmass,
        },
        new Body()
        {
            // Neptune
            x = 1.53796971148509165e+01,
            y = -2.59193146099879641e+01,
            z = 1.79258772950371181e-01,
            vx = 2.68067772490389322e-03*DaysPeryear,
            vy = 1.62824170038242295e-03*DaysPeryear,
            vz = -9.51592254519715870e-05*DaysPeryear,
            mass = 5.15138902046611451e-05*Solarmass,
        },
    };

      _pairL = new Body[(bodyCount * (bodyCount - 1) / 2)];
      _pairR = new Body[(bodyCount * (bodyCount - 1) / 2)];
      var pi = 0;
      for (var i = 0; i < bodyCount - 1; i++)
        for (var j = i + 1; j < bodyCount; j++) {
          _pairL[pi] = _bodies[i];
          _pairR[pi] = _bodies[j];
          pi++;
        }

      double px = 0.0, py = 0.0, pz = 0.0;
      foreach (var b in _bodies) {
        px += b.vx * b.mass; py += b.vy * b.mass; pz += b.vz * b.mass;
      }
      var sol = _bodies[0];
      sol.vx = -px / Solarmass; sol.vy = -py / Solarmass; sol.vz = -pz / Solarmass;
    }

    public void Advance(double dt) {
      var length = _pairL.Length;
      for (int i = 0; i < length; i++) {
        Body bi = _pairL[i], bj = _pairR[i];
        double dx = bi.x - bj.x, dy = bi.y - bj.y, dz = bi.z - bj.z;
        double d2 = dx * dx + dy * dy + dz * dz;
        double mag = dt / (d2 * Math.Sqrt(d2));
        bi.vx -= dx * bj.mass * mag; bj.vx += dx * bi.mass * mag;
        bi.vy -= dy * bj.mass * mag; bj.vy += dy * bi.mass * mag;
        bi.vz -= dz * bj.mass * mag; bj.vz += dz * bi.mass * mag;
      }
      foreach (var b in _bodies) {
        b.x += dt * b.vx; b.y += dt * b.vy; b.z += dt * b.vz;
      }
    }

    public double Energy() {
      double e = 0.0;
      for (int i = 0; i < bodyCount; i++) {
        var bi = _bodies[i];
        e += 0.5 * bi.mass * (bi.vx * bi.vx + bi.vy * bi.vy + bi.vz * bi.vz);
        for (int j = i + 1; j < bodyCount; j++) {
          var bj = _bodies[j];
          double dx = bi.x - bj.x, dy = bi.y - bj.y, dz = bi.z - bj.z;
          e -= (bi.mass * bj.mass) / Math.Sqrt(dx * dx + dy * dy + dz * dz);
        }
      }
      return e;
    }
  }
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
.NET SDK 6.0.101
Host Version: 6.0.1;
Commit: 3a25a7f1cc
<ServerGarbageCollection>true


Tue, 10 May 2022 03:46:35 GMT

MAKE:
cp nbody.csharpcore-8.csharpcore Program.cs
cp Include/csharpcore/tmp.csproj .
mkdir obj
cp Include/csharpcore/project.assets.json ./obj
/usr/bin/dotnet build -c Release --no-restore --no-self-contained -r ubuntu-x64 
Microsoft (R) Build Engine version 17.1.1+a02f73656 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  tmp -> /home/dunham/all-benchmarksgame/benchmarksgame_i53330/nbody/tmp/bin/Release/net6.0/ubuntu-x64/tmp.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:03.25

5.00s to complete and log all make actions

COMMAND LINE:
/usr/bin/dotnet ./bin/Release/net6.0/ubuntu-x64/tmp.dll 50000000

PROGRAM OUTPUT:
-0.169075164
-0.169059907